Implementing the Big Catch-Up initiative in Mozambique: a qualitative assessment of implementation barriers, equity enablers, and lessons for routine immunization

In many parts of the world, a child's first year of life is meant to be a time of protection. Health systems are designed to deliver a series of vaccines that shield young bodies from diseases like polio, measles, and whooping cough. These shots are usually given at fixed health centers or during scheduled visits to the community. However, when major disruptions occur—such as a global pandemic, civil unrest, or natural disasters—these regular visits stop. Children who miss these appointments do not just fall behind; they become "zero-dose" children, meaning they have received none of the essential vaccines at all. Without intervention, these children remain vulnerable, and the gap between those who are protected and those who are not widens. The challenge for health officials is not just to know that these children exist, but to find them in remote villages, displaced camps, or areas where trust in the system has broken down, and to bring the vaccines to them.

In 2024, Mozambique launched a major effort called the "Big Catch-Up" to address this exact problem. The goal was to locate and vaccinate children who had missed doses during the years of the pandemic, particularly those born between 2019 and 2022. To understand how this massive operation worked on the ground, a team of researchers from Mozambique's Ministry of Health, universities, and international partners like UNICEF and the World Health Organization conducted a deep dive into the process. They traveled to seven different provinces, ranging from conflict zones with displaced populations to remote rural areas, to listen to the people who planned the campaigns and the families who received them. Their work reveals that finding missed children is not a matter of simply sending out more teams; it requires a flexible, human-centered approach that adapts to the specific realities of each community.

The researchers gathered their insights by speaking with hundreds of people. They conducted 273 interviews and held 11 group discussions with 55 participants across the country. These participants included national health managers, district coordinators, health workers, and community leaders. By combining these conversations with a review of official documents, the team pieced together a clear picture of what made the initiative succeed and where it struggled. They found that the most effective campaigns were not the ones that followed a rigid, one-size-fits-all plan from the capital. Instead, success depended on local leaders who could take information about their specific area and turn it into a practical plan. In the province of Sofala, for example, teams held planning meetings that included everyone from fixed health posts to mobile outreach workers. This ensured that everyone understood the route, the resources, and the goal before they ever left the office.

A critical part of this success was the role of the community itself. The researchers learned that health workers could not simply arrive and expect families to welcome them. Trust had to be built first. In many places, the campaign succeeded because it relied on trusted local figures—community health workers, religious leaders, and village elders—to spread the word. These individuals acted as bridges, explaining the importance of the vaccines and addressing fears. In areas where people were displaced or where rumors were spreading, these trusted voices were essential. However, the study also noted that in some locations, particularly where people had been forced to flee their homes due to conflict, misinformation remained a significant barrier. In these settings, even well-intentioned efforts faced resistance from families who did not trust the system or who had been misled by false information.

To find the children who had never been vaccinated, the teams had to go beyond the official records kept at health clinics. Paper registers and digital databases often missed children who had never visited a clinic or whose families had moved. The solution was a mix of old and new methods. Health workers used the existing records as a starting point but then combined them with local knowledge. Community health workers helped map out neighborhoods and identify households that were not on any official list. This process allowed teams to pinpoint exactly where the "zero-dose" children were living. Once identified, the delivery strategy changed to meet the need. In remote areas, teams set up mobile brigades that traveled to specific gathering points like markets or schools. In other cases, they went door-to-door. This flexibility meant that services reached families who would otherwise have been left behind, extending the reach of the health system into places it rarely visited.

The researchers also observed how the teams managed their data in a country where internet connections are often unreliable. Rather than waiting for a perfect digital system, the teams used a hybrid approach. They recorded vaccination details on paper forms during the day, whether at a fixed post or in a remote village. Later, when they returned to a location with electricity and internet access, they entered that data into digital systems. This method ensured that no information was lost, even when technology failed. It allowed supervisors to see where the teams were making progress and to adjust their plans quickly. While this system was not perfect, and delays in reporting did happen, it proved to be a practical way to keep the campaign moving forward without being held back by infrastructure limitations.

Despite these successes, the study highlighted significant challenges that threatened to slow down the work. There was a shortage of health workers, and many of those available were already stretched thin by their regular duties. Training for the new campaign tools was sometimes too short to cover the complexity of the tasks, leaving some workers feeling unprepared. Logistical issues, such as poor road conditions and delays in fuel or funding, made it difficult for supervisors to visit the field and provide support. These operational hurdles meant that even the best plans could not always be executed perfectly. The researchers emphasized that without addressing these underlying issues, the gains made during the catch-up campaign might not last.

The ultimate lesson from Mozambique's experience is that reaching the most vulnerable children requires more than just a campaign; it requires a shift in how health systems operate. The study suggests that the strategies used to find missed children during the Big Catch-Up should become a normal part of routine health services. This means that community mapping, local planning, and the engagement of trusted leaders should not be temporary fixes but permanent features of the system. By integrating these approaches, health systems can ensure that no child is left behind, even when the next crisis arrives. The work in Mozambique shows that when health systems adapt to the reality of the communities they serve, they can overcome even the deepest barriers to care.